Shock absorber

ABSTRACT

A rolling bellows of a shock absorber incorporating a damper unit is sealingly secured between a housing of the damper unit and a concentric cap encircling a piston rod extending from the damper unit. Sealing attachment is effected by two clamping rings which are dimensioned relative to the housing and the cap so that on sliding assembly the bellows material is compressed. The outer clamping ring may serve as a shield protecting all outwardly facing bellows surfaces.

te State s atent BeBaan et a1.

SHOCK ABSORBER Inventors: Johannes Jasper DeBaan; Adolf Adrian, both ofEnnepetal, Germany Flrma August Bilstein, Ennepetal-Altenvoerde, GermanyFiled: Oct. 22, 1971 Appl. No.: 191,872

Assignee:

Foreign Application Priority Data Nov. 2, 1970 Germany P 20 53 826.5

11.8. C1 188/298, 188/315, 188/322 Int. Cl. 860g 11/26 Field of Search188/298, 314, 315,

References Cited UNITED STATES PATENTS 6/1962 Jackson 188/315 X PrimaryExaminer-M. Henson Wood, Jr. Assistant ExaminerMichae| Mar Attorney-KarlF. Ross [57] ABSTRACT A rolling bellows of a shock absorberincorporating a damper unit is sealingly secured between a housing ofthe damper unit and a concentric cap encircling a piston rod extendingfrom the damper unit. Sealing attachment is effected by two clampingrings which are dimensioned relative to the housing and the cap so thaton sliding assembly the bellows material is compressed. The outerclamping ring may serve as a shield protecting all outwardly facingbellows surfaces.

8 Claims, 2 Drawing Figures a- -z' 1 tom SHOCK ABSORBER BACKGROUND OFTHE INVENTION This invention relates to shock absorber incorporating adamper unit, and wherein a rolling bellows which is to be filled with afluid has its one end sealingly fastened by a clamping ring to an outerhousing tube of the damper unit and has its other end sealingly fastenedto a concentric cap connected to a piston rod extending from the damperunit.

DESCRIPTION OF THE PRIOR ART In rolling bellows mountings for such legsit is known to deform the housing tube of a damper unit, the rollingbellows and a support piece pushed over them to a smaller diameter bymangetic force. However, in this type of assembly there is a danger offolds forming in the three structural elements which are jointly reducedin dameter.

It is further known to slide a clamping ring on to a rolling bellowswhich has been drawn over a housing tube of a damper unit and forexample with the aid of an outer mandrel tool to deform the assembly sothat the housing tube, the rolling bellows and the clamping ring have alarger diameter as compared to the preassembled state. After thisincrease in diameter, the rolling bellows is pressed outwardly againstthe housing tube by the clamping ring as well as by its own stress. Withthis rolling bellows mounting, in order to avoid too high an additionalcompression force by the clamping ring, a suitable choice of materialfor the latter, or a suitable limit to the diameter incrase, must bemade.

SUMMARY OF THE INVENTION Consequently, the present invention isconcerned with the problem of providing a rolling bellows mounting whichinvolves simple attachment means, which is particularly easy to producewith reliable sealing of the rolling bellows at its clamped areas, andwhereby currently available damper units can be used without anyconstructional alterations and can be fitted into the shock absorber.

In accordance with the invention there is provided a shock absorbercomprising a damper unit externally defined by a housing tube; a pistonrod extending outwardly of the housing tube; a cap secured to saidpiston rod and concentric with respect to the damper unit; and a rollingbellows arranged to be filled with a fluid and having its ends sealinglyattached by first and second clamping rings to said housing tube and tosaid cap respectively. The clamping rings, before assembly, in the unithave internal radii which exceed the external radii of the housing tubeand cap respectively by less than the wall thickness of the rollingbellows, and on assembly are force fitted over the housing tube and capto elampingly compress the bellows ends therebetween.

The appropriate selection of the internal radii of the unsssembledclamping rings relative to the external radii of the cap and of thehousing tube, taking into account the wall thickness of the rollingbellows, means that after they have been pushed into the tight clampedposition the clamping rings and cap and housing tube are pressedsufficiently strongly against both sides of each end of the rollingbellows, to achieve the sealing seat. No mechanical distortion of themetal parts is necessary and the attachment of the rolling bellows iseffected at the same time as the fitting of the damper unit by the useof a simple pusher for sliding together the clamping rings and the capand housing tube.

According to a preferred feature of the invention, the second clampingring which presses the rolling bellows on to the cap is a protectivetube which covers the outwardly facing bellows surfaces. Thisarrangement, which is easy to attain by extending the clamping ringaxially, means that the bellows is protected over its entire length fromadverse mechanical and chemical influences. Small stones and salt waterspray thus cannot cause premature wear of the shock absorber whenmounted on a vehicle through damage to the rolling bellows. If the axiallength of the protective tube corresponds to the length of stroke of theleg, then the rolling bellows can be reliably protected in allpositions, even in its maximum extended position.

According to another preferred feature of the invention, the shockabsorber includes a filler connector for filling or emptying the bellowswherein the filler connector is tightly screwed into the part of the capwhich is covered by the rolling bellows. On tightening of the fillerconnector, the material of the cap is drawn into the rubber bellows inthe region of the hole so that a satisfactory seal is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention willnow be described in greater detail with reference to the accompanyingdrawing, in which:

FIG. 1 is a longitudinal sectional view through a shock absorberaccording to the invention; and

FIG. 2 shows a clamping ring before assembly in the shock absorber legof FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT The shock absorber shown in FIG.1 comprises a damper unit 13 defined by an outer tube 12 filled withdamping fluid. The leg is fastened, for example to a wheel axle of avehicle, by means of a securing eyelet 14 fitted to the lower end of thetube 12, a rubber buffer 15, and a sleeve 16. A piston rod 17 projectssealingly from the upper closed end of the tube 12. Inside the damperunit 13 the piston rod 17 carries a damping piston (not shown). Theouter end of the piston rod 17 is coupled to the chassis of the vehicleby means of several fastening elements. These elements comprise rubberrings 18 which are pushed over a spacing collar 1 encircling the pistonrod 17. The lower rubber ring lies on a thrust ring 2 and is pressed bythe upper rubber ring against the thrust ring by tightening nuts 19which act through a clamping ring 20. The nuts 19 can be screwed downand braced against each other on a thread formed on the upper end of thepiston rod 17, if necessary by clamping the piston rod 17 station ary bymeans of a key fitted into a square recess 21 in the end of the pistonrod. The position of the thrust ring 2 on the piston rod 17 isdetermined by a plate 4 which, in turn, is secured by a circlip 5against displacement in the direction towards the tube 12. The thrustring 2 is pressed on to a cap 6 and thereby clamps an annular sealingring 3 so that a satisfactory sealing of the piston rod 17 is achieved.The thrust surfaces 2 of the thrust ring are so angled that they pressthe sealing ring 3 against the junction betweenthe piston rod 17 and therim of the hole through the cap 6.

The cap 6, which may be made of sheet metal, encircles the piston rod 17and in the compressed state of the shock absorber encircles the upperend of the outer tube 12 of the damper unit. The cap 6 supports one end9" of a rolling bellows 9, the end which lies radially further from thepiston rod 17. The other end 9' of the bellows is attached to the upperend of the outer tube 12. The rolling bellows end 9" is pressed by aclamping ring against the cap 6, while the rolling bellows end 9' ispressed by a clamping ring 7 against the upper end of the outer tube 12.The upper end of the tube 12 is provided in its otherwise smooth andperfectly cylindrical clamping surface free from projections withannular grooves 8 into which the material of the rolling bellows isforced so as to provide a better sealing connection which is also moresecure against displacement.

The rolling bellows 9 which is made of resilient material, rubber, andwhich can be made for example a cylindrical tube is inverted at its end9" so that this end of the bellows is thereby radially more remote fromthe piston rod than the end 9. In the event of the piston rod 17 havingtravelled fully into the damper unit, the end 9" of the bellows liesapproximately at the level of the rolling bellows end 9'. The bellowssurfaces which face outwardly after the end 9" of the bellows has beenturned up are protected by the clamping ring 10' which forms aprotective tube 10, so that after mounting of the shock absorber on avehicle these surfaces cannot be mechanically damaged by flying stonesor chemically destroyed by upwardly spraying salt water. The protectivetube 10 is sufficiently long that it protects the rolling bellows evenwhen the shock absorber has been extended to its fullest extent.Consequently, in the compressed state of the shock absorber the lowerend of the protective tube 10 extends down to the vicinity of the lowerattachment means l4, l5, 16 of the shock absorber. The clamping rings 7and 10' and the cap 6 are provided at their ends which press on to therolling bellows with out-turned rims 7, 7" and 10" and an inturned rim 6respectively, by which excessive stress on the rolling bellows isavoided, particularly when assembling the shock absorber.

A filler connector 11 is sealingly screwed tightly into the cap 6 in theregion covered by the rolling bellows 9. The nipple 11 of the fillerconnector is screwed in and is tightened so strongly by an associatednut that the material of the cap 6 in the region of the thread of thefiller connector is distorted and drawn into the rolling bellows 9. Thisseal is, in the same way as the seal achieved by the clamping rings 10and 7 and by the thrust ring 2 above the sealing ring 3, so good that onfilling the rolling bellows 9 and the space enclosed by the cap 6 with afluid, for example compessed air or an oil which does not attack therolling bellows material, the piston rod 17 is forced upwardly so thatthe level of the parts, e.g., wheel axle and vehicle chassis, betweenwhich the shoek absorber is mounted can be adjusted by filling the legto different degrees.

The clamping ring 7 shown on an enlarged scale in FIG. 2 has an internalradius R which exceeds the external radius r of the outer tube 12 byless than the noncompressed wall thickness w of the bellows 9. itscrosssectional shape corresponds to that of the outer pipe 12 and itsrims 7 7" are out-turned for the purpose mentioned above.

The method of producing the rolling bellows fastening is as follows. Theouter tube 12 of the damperunit,

which can be filled with damping fluid and assembled in the shockabsorber in its finished state, is provided at its upper end, asmentioned above, with two annular grooves 8 by which an improvedsecurement of the rolling bellows 9 to the outer pipe 12 is achieved.The clamping ring 7 is first pushed over the end 9' of the bellows andthe outer tube 12, or the whole damper unit 13, is pushed with a pusherdevice into the bellows until the upper end of the outer tube 12 islevel with the rim of the end 9' of the bellows or the clamping ring 7.By appropriate dimensioning of the internal radius R of the clampingring 7 and of the radius r of the outer tube 12, the rolling bellows 9is thereby strongly compressed. Due to this fitting the internal radiusof the clamping ring 7 is slightly increased while the external radiusof the outer tube 12 is slightly reduced. These alterations to thedimensions are determined only by the materials of the interfittingstructural parts and by their pliability and no special steps to alterthe shape of the parts for improved attachment are required.

After inversion of the end 9" of the rolling bellows, the cap 6 ispushed in up to a predetermined depth x. After that, the protective tube10 is pressed on to the cap 6 by way of the bellows, the cap and tubebeing slightly distorted owing to their comparatively small wallthicknesses of about 1 mm. The tube diameter may increase for example byabout 1 mm and the cap diameter can be reduced by about 1mm.

In order to obtain a better sliding of the parts when fitting themtogether they may be provided with slide means, for example on theclamping surface of the protective tube 10 or of the outer tube 12.

We claim:

1. A shock-absorber leg comprising a damper unit defined by a housingtube; a piston rod extending outwardly of the housing tube; a capsecured to said piston rod and concentric with respect to the damperunit; and a rolling bellows arranged to be filled with a fluid andhaving its ends sealingly attached by first and second clamping rings tosaid housing tube and to said cap respectively, the clamping ringsbefore assembly in the leg having internal radii which exceed theexternal radii of the housing tube and cap respectively by less than thewall thickness of the rolling bellows, the clamping rings on assemblybeing force fitted over the housing tube and cap to clampingly compressthe bellows ends therebetween, said second clamping ring being aprotective tube and covering the outwardly facing bellows surfaces.

2. A shock-absorber leg according to claim 1, wherein the axial lengthof the protective tube corresponds to the length of stroke of the leg.

3. A shock-absorber leg according to claim 1, wherein the clamping ringsand the cap are outwardly and inwardly curved respectively at their rimswhich press against the bellows.

4. A shock-absorber leg according to claim 1, including a fillerconnector for filling or emptying the bellows wherein the fillerconnector is tightly screwed into the part of the cap which is coveredby the rolling bellows.

5. A shock-absorber leg according to claim 1, wherein the rollingbellows, the cap and the housing tube are provided with slide means onthe clamping surfaces before being interfitted. 1

6. A shock-absorber leg comprising a damper unit defined by a housingtube; a piston rod extending outwardly of the housing tube; a capsecured to said piston rod and concentric with respect to the damperunit; and a rolling bellows arranged to be filled with a fluid andhaving its ends sealingly attached by first and second clamping rings tosaid housing tube and to said cap respectively, the clamping ringsbefore assembly in the leg having internal radii which exceed theexternal radii of the housing tube and cap respectively by less than thewall thickness of the rolling bellows, the clamping rings on assemblybeing force fitted over the housing tube and cap to clampingly compressthe bellows ends therebetween, said housing tube having annular groovesin its clamping surface.

7. A shock absorber comprising a damper unit having an external housingtube of smooth cylindrical configuration free from projections; a pistonrod extending outwardly axially from said housing tube; a cap secured tosaid piston rod and coaxial with said damper unit; a rolling bellowsadapted to be filled with a fluid and having a first end fitting oversaid housing tube and a second end fitting over said cap; and a pair ofsheet metal clamping rings fitted over each end of said bellows forrespectively connecting same to said housing tube and said cap undercompression, at least said ring surrounding said first end of saidbellows retaining same against said housing tube solely by elasticdeformation of the last mentioned ring, said bellows and said housingtube, said clamping rings having internal radii which exceed theexternal radii of said housing tube and said cap respectively by lessthan the wall thickness of said bellows.

8. A shock absorber as defined in claim 7 wherein the clamping rings andsaid cap are outwardly and inwardly curved respectively at their rimswhich press against said bellows.

l t t

1. A shock-absorber leg comprising a damper unit defined by a housingtube; a piston rod extending outwardly of the housing tube; a capsecured to said piston rod and concentric with respect to the damperunit; and a rolling bellows arranged to be filled with a fluid andhaving its ends sealingly attached by first and second clamping rings tosaid housing tube and to said cap respectively, the clamping ringsbefore assembly in the leg having internal radii which exceed theexternal radii of the housing tube and cap respectively by less than thewall thickness of the rolling bellows, the clamping rings on assemblybeing force fitted over the housing tube and cap to clampingly compressthe bellows ends therebetween, said second clamping ring being aprotective tube and covering the outwardly facing bellows surfaces.
 2. Ashock-absorber leg according to claim 1, wherein the axial length of theprotective tube corresponds to the length of stroke of the leg.
 3. Ashock-absorber leg according to claim 1, wherein the clamping rings andthe cap are outwardly and inwardly curved respectively at their rimswhich press against the bellows.
 4. A shock-absorber leg according toclaim 1, including a filler connector for filling or emptying thebellows wherein the filler connector is tightly screwed into the part ofthe cap which is covered by the rolling bellows.
 5. A shock-absorber legaccording to claim 1, wherein the rolling bellows, the cap and thehousing tube are provided with slide means on the clamping surfacesbefore being interfitted.
 6. A shock-absorber leg comprising a damperunit defined by a housing tube; a piston rod extending outwardly of thehousing tube; a cap secured to said piston rod and concentric withrespect to the damper unit; and a rolling bellows arranged to be filledwith a fluid and having its ends sealingly attached by first and secondclamping rings to said housing tube and to said cap respectively, theclamping rings before assembly in the leg having internal radii whichexceed the external radii of the housing tube and cap respectively byless than the wall thickness of the rolling bellows, the clamping ringson assembly being force fitted over the housing tube and cap toclampingly compress the bellows ends therebetween, said housing tubehaving annular grooves in its clamping surface.
 7. A shock absorbercomprising a damper unit having an external housing tube of smoothcylindrical configuration free from projections; a piston rod extendingoutwardly axially from said housing tube; a cap secured to said pistonrod and coaxial with said damper unit; a rolling bellows adapted to befilled with a fluid and having a first end fitting over said housingtube and a second end fitting over said cap; and a pair of sheet metalclamping rings fitted over each end of said bellows for respectivelyconnecting same to said housing tubE and said cap under compression, atleast said ring surrounding said first end of said bellows retainingsame against said housing tube solely by elastic deformation of the lastmentioned ring, said bellows and said housing tube, said clamping ringshaving internal radii which exceed the external radii of said housingtube and said cap respectively by less than the wall thickness of saidbellows.
 8. A shock absorber as defined in claim 7 wherein the clampingrings and said cap are outwardly and inwardly curved respectively attheir rims which press against said bellows.